The present invention relates to a mirror arrangement for a rear view mirror system in an article of headgear, especially for a rear view mirror system in a cycling or motorcycling helmet, although not exclusively limited thereto.
Rear view mirror systems for cycling and motorcycling helmets are known, such as the helmet shown in PCT/GB94/00485 which relates to a helmet having a solid block of light transmissive material with reflective surfaces arranged within a channel in the foam padding of a helmet. FR2631789 discloses a helmet with an open, hollow channel through the helmet over the wearer""s head. The helmet has two mirrors on the upper side of the channel and one mirror on the lower side of the channel. The mirrors direct light from behind the wearer to the wearer""s eyes. EP0007432 discloses a helmet including a series of convex lenses and an optical fibre in the helmet to enable the wearer to see behind themselves. Three of the lenses are arranged radially to the wearer""s head. The channel through the helmet is hollow and open to the air. A further helmet is known from PCT/GB96/02349 where a plurality of mirrors are arranged on a one piece mounting which is arranged in a channel in the foam padding inside the outer shell of the helmet.
The region of distinct vision of the retina of the human eye occupies approximately 6xc2x0 in terms of plane angles. In other words, without moving the eye, only objects lying in a cone of vertex angle 6xc2x0 can be distinguished clearly. It is an object of the present invention to provide an improved mirror arrangement for a rear view mirror system in an article of headgear.
According to one aspect of the invention there is provided a mirror arrangement for a rear view mirror system in an article of headgear comprising first, second and third mirrors, the first mirror comprising a concave, off axis parabolic mirror arranged, in use, adjacent the eyes of the user, the first mirror having a principal axis and an effective focal length f1, the second mirror being substantially flat and being arranged between the first and the third mirror and the third mirror comprising a convex, off axis parabolic mirror having a principal axis and an effective focal length f3, whereby the first and third mirrors have a common focus and the parabolas are related such that 1.5 f1xe2x89xa6f3xe2x89xa63f1.
In that way, the mirror arrangement of the invention allows an expanded field of view to be viewed in a contact mirror arrangement which can be located in a channel in the foam padding of the helmet without compromising the protective function thereof. The claimed range of parabola geometry provides a range of field of view from 9 to 18xc2x0. Preferably, f3=2f1 
In that way, the mirror arrangement in the helmet doubles the field of vision, in other words, the field of vision is approximately 12xc2x0. That enables a 2 metre high object to be viewed in full at a distance of 10 metres behind the user.
The second flat mirror is preferably arranged closer to the first mirror than the third mirror. That arrangement is to allow the size of the second mirror to be reduced and to increase the angle of light approach xcfx86 at the third mirror.
The first mirror is preferably arranged, in use, so that it can be viewed by both eyes of the user.
The mirrors are preferably arranged in a channel in the foam padding of a helmet. The mirrors are preferably all arranged across the top of the channel facing into the channel.
The mirrors may be formed as part of a one piece mounting. The one piece mounting may be arranged in the aforesaid channel. Preferably the one piece mounting comprises a mating formation on an edge thereof and the article of headgear includes a channel, the article of headgear having a co-operating mating formation formed along an edge of the channel, the mating formation co-operating so as to retain the mirror arrangement on the article of headgear.
According to another aspect of the invention there is provided a mounting arrangement for a rear view mirror system, the arrangement comprising an article of headgear having a channel formed therein and a mirror assembly mounted on the article of headgear so as to bridge the channel, the mirror assembly having a mating formation formed along an edge thereof, the article of headgear having a co-operating mating formation formed along an edge of the channel, the mating formations co-operating so as to retain the mirror assembly of the article of headgear. That provides a convenient way of assembling the mirror assembly into the article of headgear.
Preferably, the mirror assembly has respective mating formations formed along opposite edges thereof and the article of headgear has respective co-operating mating formations formed along opposite edges of the channel. The mating formation on the mirror assembly or article of headgear may comprise at least one protrusion and the mating formation on the other of the mirror assembly and article of headgear may comprise at least one recess, the or each protrusion fitting within the respective recess with an interference fit. In a preferred embodiment the protrusion is provided on the mirror assembly and the recess is provided on the edge of the channel in the article of headgear.
Preferably, the protrusion comprises a lug having a neck and a head, the head being larger than the neck, the recess being substantially the negative of the protrusion. The lug may be formed with a curve between the neck and the head.
In that way impact or stress to the article of headgear is dissipated through the mirror assembly via the curved lugs into the body of the article of headgear. The curved lugs reduce stress concentrations and thus reduce the risk of the mirror assembly breaking under stresses applied to the article of headgear. In the case of a helmet, impacts may be severe and the configuration of the mounting renders the mirror assembly safer than previous such systems.
Preferably, a plurality of protrusions and a corresponding plurality of recesses are provided. Most preferably a plurality of curved lug protrusions and respective mating recesses are provided.